In a typical metal oxide-hydrogen battery, such as a nickel oxide-hydrogen battery, one or more cell modules are sealed in an outer pressure vessel that contains pressurized hydrogen gas. The pressure vessel is normally formed of a high strength, corrosion resistant metal, such as Inconel, and includes a cylindrical shell with a pair of domed shaped heads welded to the open ends of the shell. It has been the practice in the past to utilize a machined metal weld ring to support the abutting edges of the shell and head during the welding operation. The typical weld ring has a generally T-shaped cross section including an annular body portion and a central radially extending flange.
To weld the head to the shell, the ring is positioned within the opposed open ends of the head and shell with the ends of the head and shell engaged with opposite surfaces of the fins. The abutting edges of the head and shell are then welded to the ring.
The weld ring, as used in the past, has been machined from a block of metal and in some cases the weld ring has also included central radial spokes. The machining of the ring from a metal, such as Inconel, is an extremely expensive procedure.
The shell and heads of the pressure vessel of a metal oxide-hydrogen battery are normally produced by a metal drawing procedure which can result in slight variations in diameter or concentricity.
The weld ring must fit precisely within the open ends of the shell and head of the vessel. If there is any substantial gap between the ring and the end of the shell or head, weld metal may spray into the battery and the sprayed metal can bridge the cells to provide a shorting path. Further, any weld metal which is deposited in the gap between the weld ring and the end of the head or shell can act as a fulcrum when the vessel is under stress due to the high internal pressure of the hydrogen gas and this can result in stressing of the vessel at the fulcrum and possible failure.
Because of the need for a precise fit between the weld ring and the shell and head, it has been the practice to machine the weld ring slightly oversized and then by trial and error further machine the weld ring to fit the head and shell. This procedure is extremely time consuming and costly due to the fact that in many cases the machining has to be done by an outside supplier.